The present invention relates to a public or pay telephone magnetic cash box switch configured to be mounted in an upper portion of the lower phone housing directly above the phone's vault area.
Conventional cash box switch arrangements are designed to detect the presence of the cash box either through mechanical or optical methods. These switches generally require the removal of the vault door and cash box for installation. For example, the arrangement in FIG. 1 is placed in the bottom of the vault area and uses an L-shaped arm to open and close a switch where the L-shaped arm is acted upon by the cash box. Such arrangements are both relatively delicate and are also relatively difficult to install.
We have recognized that the conventional switches possess other substantial disadvantages, chief among them being cost, unreliability due to fragile moving parts, susceptibility to tampering and corrosion, and temperature sensitivity. In the case of optical switches, interface electronics and/or a special chassis are required. Moreover, optical switches are affected by the physical condition of the cash box lid resulting from corrosion, dust, dirt, airborne contaminants and the like.
It is an object of the present invention to provide a low-cost magnetic cash box proximity switch which greatly simplifies installation, i.e., a switch which does not physically contact the cash box and which does not require the removal of the vault door and the cash box.
It is yet a further object of the present invention to allow for the switch to be installed by technicians who would normally not have keys which provide access to the vault area and cash box.
It is a still further object of the present invention to provide a cash box switch which utilizes non-contact magnetic techniques rather than the more conventional mechanical and optical methods so as to provide a relatively uncomplicated, reliable configuration.
In addition to being easily installed and reliable, the switch according to the present invention has the advantage of being tamper-proof, sealed and eliminating a need for power consumption.
Other advantageous features of the switch according to the present invention include a completely passive system which does not require any interface electronics or a special chassis, elimination of all moving parts except for a magnet, a switch which is downwardly compatible in place of a mechanical cash box switch, and a switch which can be retrofitted for use in existing 1D-style phone housings but can also be adapted to fit in 2D-style panel phone housing.
The foregoing objects and advantages have been achieved by providing a public telephone cash box switch using a magnet which is mountable in the portion of the lower housing directly above the phone's vault area. That is, the magnetic switch utilizes a bi-stable magnetic circuit in which the lower pole of the magnet is attracted to the phone housing with no cash box present and to the cash box lid when the cash box is installed. Proximity sensing avoids physical contact between the switch arrangement and the cash box lid.
More specifically, in a currently preferred embodiment, the switch arrangement includes a cap and a lower body containing a vertically oriented sealed reed switch and corresponding magnet for effecting the electrical switching function in which the corresponding magnet has a vertical travel of 0.050 inch. The magnet can be a Neodymium rare earth permanent magnet grade such as 33H with the distance between the reed switch contacts and the magnet chosen to minimize hysteresis in the operation of the reed switch.
The switch housing can be molded from a plastic or other suitable non-ferrous material selected for minimum friction, temperature stability, and moisture and humidity resistance. The housing unit is configured to be sealed with a compressible molded elastomer gasket to prevent dirt and moisture intrusion. The unit can be assembled with one or more screws or snapped together with interference fit posts and bores.
A flex circuit can be utilized for mounting the reed switch and making the electric connection to the wires while positioning and precisely retaining the reed switch within the switch housing. The above-mentioned elastomer sealing gasket can also be used to apply pressure to the top formed lead of the reed switch to assure its proper location within the housing.